Arnica: Seep Spring Arnica

I think this is Arnica longifolia, aka Seep Spring Arnica. Identification of arnica is difficult. Some species hybridize and reproduce assexually and develop their own charactieristics. Furthermore, I didn't identify these flowers in the field and it's always hard to identify from a photo. Still, the long shiny leaves rule out Arnica mollis (Hairy or Soft Arnica), it was growing in a large mass in a running seep, which is typical of A. longifolia.